1. Field of the Invention
The present invention relates to apparatus for determining the load applied to a wheel of a tracked vehicle by the track adjacent to the wheel.
2. Description of Related Art
It has previously been proposed to use so called "active" suspension systems to control the suspension of a tracked vehicle. "Active" suspension systems are suspension systems in which the wheels of the vehicle are connected to hydraulic actuators which can be controlled to cause motion of the wheels. The hydraulic actuators are controlled by control processors in response to various measured physical parameters. An example of such an "active" suspension system can be seen in European Patent Publication No. 0114757.
The application of active suspension to a tracked vehicle provides problems since in most active suspension systems it is necessary to measure the load transmitted by an actuator to the vehicle body. In a tracked vehicle, the load transmitted by an actuator to the tracked vehicle body comprises not only the load on the wheel transmitted from the road, but also comprises load on the wheel due to tension in the vehicle track associated with the wheel. For correct operation of the vehicle suspension system the force on the wheel due to the track of a tracked vehicle must be isolated, to allow the active suspension system to react only to loads on the wheel due to road inputs, that is to say loads on the wheel due to the interaction of the vehicle with the terrain over which it passes.